Definition 1 (Inclusion Functions) [1]} 
Consider a function \(f:\mathcal {Z} \subset \mathbb {R}^{n_z} \rightarrow \mathbb {R}^{n_x}\) . The interval function \(T^f:\mathbb {IR}^{n_z} \rightarrow \mathbb {IR}^{n_x}\)  is an inclusion function for \(f(\cdot )\) , if
\(\forall {\color {black} \mathbb {I}}\mathcal {Z} \in \mathbb {IR}^{n_z}, f({\color {black} \mathbb {I}}\mathcal {Z}) \subset T^f({\color {black} \mathbb {I}}\mathcal {Z}),\) 
